1. Field of the Invention 
The present invention relates generally to the field of barbecue grills, cookers, and smokers and, more specifically, to a new design for a smoker which allows for more evenly distributed heating and smoking of food and which can also be adjusted to act as a barbecue grill or cooker. 
2. Description of Related Prior Art 
The prior art is crowded with barbecue grills and smokers, in combination and separately. Typically, these devices use charcoal briquettes or wood as a heat source to cook food placed on a grill near the heat source. The devices are often adjustable in some manner to allow for smoking the food as opposed to grilling it over an open flame. 
Traditional smokers are constructed with the fireboxes located to the right or left of the grill and the smoker housing. In this type of construction, smoke and heat from the firebox is allowed to drift into the smoker housing through vents and thereby cooking and smoking the meat. The problem with this traditional type of smoker is that food items placed closer to the firebox smoke and cook faster than food items placed further away. This requires food items to be continually monitored and rotated on the grill to ensure even cooking/smoking of the food items. 
There are many other smoker and barbecue grill designs where the cooking  surface is positioned above the heat source. An example of these designs include the following: U.S. Pat. No. 4,094,295 to Boswell, et al; U.S. Pat. No. 4,467,709 to Anstedt; U.S. Pat. No. 4,495,860 to Hitch, et al; U.S. Pat. No. 4,962,697 to Farrar; and U.S. Pat. No. 5,359,923 to Boswell. Typically, the fireboxes and/or the grills in the aforementioned patents are adjustable to various heights depending on whether smoking or barbecue style heating is desired. Many of these inventions also contain water pans to create steam to mix with the smoke during the cooking process. 
A patent to Hastings, U.S. Pat. No. 2,666,425, describes a hooded barbecue grill with two sets of rails placed at different heights below in the grill to support a removable firebox. The upper rails are also used to support a heat deflector when the firebox is located and supported by the lower set of rails. A patent to Leech, U.S. Pat. No. 3,379,190, also discloses a barbecue pit which allows for a varying heights of the firebox. The Leech design has two fireboxes each of which is supported in a cantilever fashion from opposite sidewalls of the device. The fireboxes can be raised and lowered to vary the cooking heat at the grill level. While the Hastings and Leech design allow for adjustable firebox heights to vary temperatures at the grill, it does not allow for even distribution of smoke when smoking the food items placed on the grill. 
A patent to Bussey, U.S. Pat. No. 5,460,159, discloses a smoker/barbecue pit which allows smoking and barbecuing at the same time. This invention directs heat and smoke around and towards the grilling surface from the sides of the grilling surface. This patent also describes directing smoke and heat through opening on the sides of  the units where detachable pot warmers can be attached. 
Finally, a patent issued to Ruben, U.S. Pat. No. 5,473,979, discloses a three-chambered “smoker”. The lower chamber where the firebox is located, has a rotatable partition plate which controls and directs heat and smoke from below and catches and funnels off drippings from above. 
Some or all of the aforementioned patents and prior art attempt to direct and channel heat and smoke in order to vary the temperature and more evenly distribute the heat and smoke. This is done with shielding devices which rest between the heat source and the grilling surface and/or the shape of the hood above the grilling surface. However, none of the aforementioned patents allow heat and smoke to collect and drift upwards toward the grilling surface in an even distribution. It can be seen that there remains a need for a smoker/barbecue grill which more effectively allows for an even distribution of smoke and heat from the fire pit. 